Continuing effort for increasing the storage density for color television signals recorded by magnetic tape apparatus has led to the introduction of a series of innovations from each of which a certain contribution towards raising the storage density of information on recordings has been provided. The known techniques thus developed can be roughly classed in two catagories: the first category of solutions to the problem is concerned with raising the usable frequency bandwidth of a given magnetic tape appratus or, for a similar purpose, the lowering of the necessary relative velocity between the magnetic record medium and the magnetic transducer or transducers while maintaining the upper frequency limit at all times. By diminution of the relevant dimensions of the magnetic transducers and improvement of the magnetic qualities of the record medium, it has been possible to a certain degree to reduce still further the smallest wavelengths that can be recorded, thus leading to the above-mentioned effect.
A further technique for improving the recording quality, while at the same time holding down the requirements on the mechanical and electrical properties of the magnetic tape equipment, is the process, for a long time conventional in the art, of frequency conversion of a chrominance signal modulated on an auxiliary carrier wave so as to place the signal into a frequency band adjacent to and below the lower frequency boundary of the frequencymodulated luminance signal. Such a process is known, for example, from DE-OS No. 18 08 439.
Another process for raising the storage density in the storage of signals on a magnetic tape is described in DE-OS No. 19 35 109. There the color television signals are separated into a luminance signal and a chrominance signal, and these components are then laid down in separate recording tracks by separate recording heads. The equipment is so designed that tracks of the first and second kind overlap each other at least partly, and in order to reduce cross-talk, the core gaps of the respective magnetic heads for the first and second kinds of tracks are set at an angle to each other with respect to the plane of the magnetic tape (azimuth-offset recording).
In DE-OS No. 14 74 268, a magnetic tape equipment for recording television signals is described in which the tape moves helical around a device of which a head wheel, with two diametrically oppositely lying magnetic heads, rotates. For suppression of the cross-talk that arises in recording without intermediate space between the individual tracks, the synchronizing pulses of neighboring tracks are so disposed that even in case of deviations of the magnetic heads from the track in playback, the synchronizing of the reproduced picture is not persistently impaired. The interrelations involved in the alignment of the synchronizing pulses are also described in an article by F. T. Backers and J. H. Wissels entitled "An Experimental Apparatus for Recording Television Signals on Magnetic Tape" in Philips Technical Review, Vol. 24, No. pp. 81-83 (1962).
From DE-OS No. 26 29 706, a method for transmitting and/or recording of color television signals is also known in which the color information is compressed in time and is transmitted and/or recorded line by line during the horizontal blanking interval. In this manner a broad band luminance signal is preserved and reliable synchronization is made possible. That known method offers an improvement of the resolution with only slight color errors. The luminance information is recorded and/or transmitted during about 80% of the horizontal line scan period and the color signal is recorded and/or transmitted in time-compressed form, line by line, during the horizontal blanking interval of a normal television signal. The color signals, moreover, are recorded or transmitted during the largest part of the remaining 20% of the line scan period and during a time interval that is small compared to the interval available for transmission of the color signal, a blanking signal is transmitted of a value that indicates the hueless value of the color signals. According to an embodiment of the known method, in every second line a blanking signal is transmitted and in the lines between them a synchronizing pulse is transmitted. This process has the advantage that the amplitude errors arising in transmission and/or recording make themselves noticed in all cases as color saturation errors, but not as color hue errors. Furthermore, a sufficient degree of synchronization is made possible, and by means of the synchronizing pulses the switches necessary in reproduction for the color difference signals can be synchronized.
It is finally known from DE-OS No. 27 45 337 to reduce the bandwidth requirements in recording of broadband signals by subdividing these signals on a time division basis successively in groups of n subdivisions and to record them in a plurality of channels. This system, however, involves dynamic storage with many parallel tracks running lengthwise of the magnetic tape.